In preparing fabric material for industrial and consumer use it is often desirable to be able dye samples of the material on a laboratory scale. For example, laboratory scale dye tests are often useful for generating samples of material for selection by a purchaser prior to the placing of an order, thereby ensuring that both the purchaser and the seller are in full agreement with regard to the coloration of the fabric to be purchased. Laboratory scale dying is also of benefit in evaluating the performance of various dyes when applied to fabrics under production conditions thus permitting the entity performing the dyeing operation to select those dyes which will perform best.
As will be recognized, in order to derive meaningful comparative data, the dye testing as described above must be carried out on multiple fabric samples dyed under substantially similar test conditions. Moreover, in order to be useful, these test conditions must closely resemble actual production dying operations. It will be readily appreciated that in carrying out these evaluations, it is desirable to minimize any variability regarding the treatment of individual samples which may tend to reduce the confidence level for the tests.
It has long been recognized that the simultaneous treatment of a relatively large number of samples in a single test unit permits researchers to minimize the variability associated with multiple individual tests. However, in order for a meaningful comparative analysis of the samples to be made, each of the samples within the apparatus must, in fact, be subjected to substantially the same conditions during the test.
Since many commercial dying operations are performed at elevated controlled temperatures of between 200 and 300 degrees Fahrenheit, it is necessary to carry out dye testing in a similar environment. Accordingly, a testing apparatus is required which is capable of simultaneously subjecting multiple dye test specimens to elevated and controlled temperatures.
Prior to the present invention, the need to uniformly subject multiple samples to a high temperature environment was met primarily by enclosing fabric specimens and dye liquor within liquid tight sample containers and thereafter passing these containers through a heated bath of relatively high boiling point liquid such as, for example, a glycerin emulsion. These systems typically utilize a bath chamber which houses a rotatable sample rack capable of holding approximately twenty (20) individual sample containers. This sample rack is rotated within the bath chamber so as to intermittently pass each of the sample containers through the heated liquid bath. The bath temperature is controlled by means of several stainless steel electric immersion heaters in combination with a tap water cooling coil. The operation of the immersion heaters and tap water cooling coil is in turn controlled by a programmable logic controller based on temperature readings taken within the bath.
In operation, as each of the sample containers is passed through the heated bath, the temperature of the dye liquor and fabric sample housed within the container tends to equilibrate with the temperature of the bath. Thus, the temperature of the samples may be driven upwards to a level approximating that of production dying operations. Moreover, the rotating action provides contacting agitation between the dye liquor and the sample, thereby simulating the mechanical action of a production dyeing operation.
As will be recognized, while the use of a heated bath may provide a uniform temperature environment for all samples, a number of problems are also associated with such a process. For example, the potential for corrosion is significant in such liquid processes thereby necessitating the initial use of high cost corrosion resistant materials for construction. Further, during the life of the equipment, corrosion damage which does occur may give rise to costly and time consuming repair or replacement of the damaged portions.
In an attempt to eliminate some of the undesirable aspects of liquid bath equipment, there has been some effort in the industry to replace the heated liquid bath with radiant heating elements. One such heating device incorporates the use of a vertically oriented rotatable holding disk which intermittently reverses its direction of rotation so as to move the sample containers back and forth in front of a plurality of radiant heating elements oriented across the ceiling of the unit. Based on the evaluation of dye liquor temperature measured within the sample container in relation to a preprogrammed set point, adjustments are made to the level of power supplied to the radiant heaters so as to alter the rate of temperature increase or decrease. Cooling air may also be introduced through a side duct. While this design has eliminated the use of high temperature liquids through the introduction of radiant heaters, an apparatus which provides such benefits while at the same time further reducing variation in treatment conditions between samples is desirable and thus provides a useful advancement over the present art.
In addition to dye sample testing, those devices described above have also been used to measure color fastness of previously dyed materials. As will be appreciated, by exposing previously dyed fabric samples to controlled temperature and detergent conditions, multiple washing cycles can be simulated. Thus, the performance of various dyed materials can be compared. However, as with sample dying evaluations, the ability to make valid comparisons is dependent upon uniformity with respect to treatment conditions.